CSS Variables not work with custom property fallback values

I am declaring a custom property in :root like below, but my color not work for me. What I am wrong?

:root {
    --color-primary: var(--color-primary, #ffc107);
}
body {
    background-color: var(--color-primary); // background color not work
}

>Solution :

Declaring css variables should be like this:

:root {
    --color-primary: #ffc107;
}
body {
    background-color: var(--color-primary);
}